He dodged through pa.s.sages, rounded turns, leaped over stalagmites. Once he had to crawl on his hands and knees under water-smooth limestone, pushing his rifle ahead of him.

And all the time he was catching up to the end of the light. The radius of illumination narrowed as the batteries failed, increasing the danger of stumbling into a sudden crevice. Outside, the flashlight would have been rejected long ago as a source of light. But far underground, with no other light of any kind, it was still useful.

Running more slowly now, at a stumbling dogtrot, he broke into a cave larger than any he had seen since the first one, at the end of the pa.s.sage from the Black Buddha. The feeble light failed to reach the opposite wall.

Rick stopped, panting for breath. He knew he had to rest. He found a natural seat next to a twisted pillar of limestone and sat down.

The light slowly faded until there was only the dimmest of red tints to the bulb, and then that vanished too, and he was again in total darkness. As he watched the light fade, he remembered the infrared. Now he got the gla.s.ses from the case and put them on. He took the camera out and adjusted the handstrap so it could be carried like a satchel. But he didn't turn on the light just yet. The battery had to be conserved at all costs. Because....

He swallowed hard. Because when the battery for the infrared light ran down, there would be nothing but darkness. Darkness would mean feeling his way through the limestone tangle, and he realized fully that he would not get far before death claimed him in the form of a yawning canyon in the limestone rock. He had pa.s.sed many of them.

He set his jaw. That was ten hours away, because the battery would last that long. Ten hours was a long time if used wisely.

He closed his eyes and leaned back, dead tired. He dozed off.

Rick was never sure what awakened him, because there was no noise. It may have been the light on eyes made sensitive by ultimate blackness.

But could a single candle have that much effect?

The candle was carried by a man. A Tibetan. The candle was in a tin container, punched full of holes. That was to keep it from being blown out in case of a draft, although there was little or no draft in the caverns.

When Rick opened his eyes the man was walking straight across the floor of the big cave, noiseless as a cat in feet wrapped in quilted cloth.

The miracle was that Rick didn't cry out on seeing another human.

He sat frozen, watching the man. Then, as the stranger reached the far side of the cave, Rick came to life. If he lost this man, who obviously knew his way around, he was finished! Working at top speed he untied his shoelaces and slipped off his shoes. Then, in stocking feet, he padded silently across the floor.

The candle was his guide. He didn't need the infrared beam yet. He would follow the candle, and if it led him right into the hands of the enemy, that was better than perishing alone of hunger in the blackness of the inner caves.

As he went, wary of a backward look by his quarry, he put his rifle under his arm and fumbled to tie a knot in his laces. It took time, since he was carrying the camera in one hand now. When he finally managed, he draped the shoes around his neck.

A dozen times he had been on the verge of abandoning the rifle as useless extra weight. Now he was glad he had held onto it.

Ahead, the candlelight bobbed and turned as the Tibetan, unaware that he was being followed, made his way through the caverns. Rick followed at a safe distance, close enough to avoid being left behind by a sudden turn.

There was a new feeling in the air suddenly, a feeling of s.p.a.ce and of wetness. Rick sniffed. There was an odor, too, like decaying leaves, although much weaker. His hopes brightened. Was the Tibetan leading him out of the caves?

Then, so suddenly that he almost slipped from the edge, the path took him to a narrow ledge above a body of water of some kind.

The Tibetan was making his way along the ledge, candle held high in a search for something. When Rick switched on the infrared light for a moment, the incredible scene leaped to his eyes from the darkness. From under his feet a lake stretched away, its farther sh.o.r.e beyond the eight-hundred-yard range of the infrared light. He turned the light back and forth, seeking the end of the amazing body of water. But there was nothing except the sh.o.r.e on which he stood.

The water was dead calm. Not a ripple disturbed the gla.s.sy surface. He shot the invisible light straight down, and the water was so deep it looked black.

With a sudden start he realized he might lose the Tibetan candle bearer.

He hurried after him, using the infrared light because the candle was too far away now to show him the path. With the gla.s.ses on, using the infrared light was just like using a powerful searchlight.

Far ahead, the candle stopped moving. Rick now proceeded more cautiously, and he switched off the infrared light in case the Tibetan should look back and possibly spy the glowing filament of the lamp.

The man was stooping over something, the candle resting on the stone next to him. Rick switched the light on, then off again. And he broke into a silent run. During the second the light had been on he had seen that the Tibetan was untying a boat!

He had an instant to make a decision. He reached a spot a few feet behind the preoccupied stranger, who was having trouble with the rope knot, and put the infrared camera down on the stone. Then, gripping the rifle firmly, he walked right up to the man.

"Hands up," he growled.

The Tibetan screamed.

He whirled, eyes wide with astonished fright, and he didn't even see the rifle. He swept an enormous knife from his belt and leaped!

Rick stumbled backward, and as he did, he realized that he couldn't shoot. He still needed the man for a guide. He swung the rifle, barrel first.

It was just as effective as it had been when he swung on Worthington Ko.

The barrel connected with an audible _thunk_. The Tibetan fell forward on his face.

Frightened out of his wits, Rick rolled him over, pulled aside the sheepskin coat he wore and put his ear on the man's chest. Then he sighed with relief. He hadn't swung too hard. For a moment he had feared that the blow had killed the man. And that would have been almost as effective as holding the rifle barrel to his own head, because he still had no idea of where to go without the guide.

He debated for a moment, then lifted the Tibetan, dragged him to the boat and dumped him in. It was a flat-bottomed craft with blunt ends and primitive oar-locks. The oars were poles with round disks of wood on the ends.

He collected the candle and the camera, placed them on a thwart, and went to work on the rope. It was reeved through an iron ring that jutted from the stone. The sight gave him heart. Where there was iron, men came often. At least he was sure that held true in this case. But his victory had spurred him on and he didn't want to sit quietly and wait. He wanted to keep going.

He untied the knot, blew out the candle, shipped the oars and pushed off. Something was on the other side of this Lake of Darkness. He couldn't imagine what, but he intended to find out!

CHAPTER XVII

Through a Pair of Dark Gla.s.ses

Somewhere, perhaps, beyond the Lake of Darkness, was Long Shadow.

Rick felt certain of it. The Tibetan who lay unconscious at his feet had been going somewhere. He had walked steadily and purposefully, with some definite destination in mind. What was more logical than to a.s.sume that the Tibetan had been heading for the hidden plant where heavy water was being produced?

Once the plant was found, Long Shadow would be found there, also. Even if he were not there at the moment, he would come. And when he did, Rick intended to do something about it. He had no definite plans. He only knew that somehow he would force Long Shadow to unlock the gate to the outer world.

His oars dipped rhythmically as he pulled out into the lake. The infrared light was directed toward a jutting edge of limestone on the sh.o.r.e he had just left. He was using the rock formation as a marker so he could steer a straight course.

He wondered about his friends. Were they lost, too? Or had they managed to keep to the right trail by following the tiny drops of candle wax?

The odd tin candleholder explained why there wasn't more wax to follow.

The holder caught most, but not all of the drippings.

The rocky sh.o.r.e of the underground lake receded rapidly. Rick stopped rowing and turned, switching the infrared light toward the direction in which he was heading. He could see the opposite sh.o.r.e now, but dimly.

Knowing that the infrared light was effective at eight hundred yards, he estimated the lake to be about twelve hundred yards wide. That was over three-fifths of a mile.

When he shot the light up and down the lake, he saw nothing but the black water. That meant the lake was more than sixteen hundred yards long. He turned the light upward and surveyed the ceiling. It was irregular, varying in height from a dozen feet to over two hundred. In one place, the ceiling came down to within a few feet of the black water.

It was an eerie place. Rick's quick imagination turned him into the mythical Charon, who ferried the dead across the River Styx into Hades.

He grinned mirthlessly. The limp figure of the Tibetan gave substance to the picture.